Semipermeable membranes play an important part in industrial processing technology and other commercial and consumer applications. Examples of their applications include, among others, biosensors, transport membranes, drug delivery systems, water purification devices, supported catalysts, including supported enzyme catalysts, and selective separation systems for aqueous and organic liquids carrying dissolved or suspended components.
Generally, semipermeable membranes operate as separation devices by allowing certain components of a liquid solution or dispersion of solvent and one or more solutes to permeate through the membrane while retaining other components in the solution or dispersion. The components that permeate or are transmitted through the membrane are usually termed permeate. These components may include the solution or dispersion solvent alone or in combination with one or more of the solution or dispersion solutes. The components retained by the membrane are usually termed retentate. These components may include either or both of the solution or dispersion solvent and one or more of the solution or dispersion solutes. Either or both of the permeate and retentate may provide desired product.
The industry has, for convenience, categorized these semipermeable membranes as microfiltration, ultrafiltration, nanofiltration or reverse osmosis membranes. These categories do not have rigid definitions. Most definitions available in the industry arrange the membranes according to properties and function. For example, the microfiltration and ultrafiltration membranes are often defined by their pore sizes. Typically, these membranes contain recognizable pores of sizes from 0.1 to 10 microns and 1 nm to 0.1 micron respectively. Nanofiltration (NF) and reverse osmosis (RO) membranes, in contrast, are most often regarded as not containing recognizable pores. Instead, NF and RO membranes are believed to transmit liquid permeate through void spaces in the molecular arrangement of the material making the membrane barrier layer. NF membranes typically are used, for example, to fractionate monovalent ions from divalent ions or to fractionate small organic compounds from other small organic compounds (monosaccharides from disaccharides, for example) or salts from organic compounds. RO membranes generally retain all components other than the permeating liquids such as water, with certain exceptions such as weakly ionizing HF, which tends to permeate with water through RO membranes. Under certain circumstances, the RO membranes can also be used to separate and/or fractionate small organic molecules.
RO membranes are often found in industrial applications calling for concentration of mixtures of inorganic salts, or concentration of mixtures of small, very similar organic molecules. RO membranes are used foremost for desalination either of municipal or well water or of seawater. These membranes are also typically used in recovery operations such as mining, spent liquor recovery from industrial processing and general industrial applications. The RO membranes function by retaining the solution solute, such as dissolved salts or molecules, and allowing the solution solvent, such as water, to permeate through the membrane. Commercial RO systems typically retain greater than 99% of most ions dissolved in a solvent such as water.
In contrast, NF membranes are often found in industrial applications calling for separation of one small compound from another. For example, NF membranes are used foremost for separation of alkaline salts from alkaline earth salts such as separation of mixtures of sodium and magnesium chlorides. Some NF membranes function by retaining the double charged ions while allowing the singly charged ions (with their corresponding anions) to permeate with the solvent.
RO and NF membranes are typically characterized by two parameters: permeate flux and retention ability. The flux parameter indicates the rate of permeate flow per unit area of membrane. The retention ability indicates the ability of the membrane to retain a percentage of a certain component dissolved in the solvent while transmitting the remainder of that component with the solvent. The retention ability is usually determined according to a standard retention condition.
RO and NF membranes are typically operated with an appropriate pressure gradient in order to perform the desired separations. When functioning to separate, the filtration process using a RO or NF membrane overcomes the osmotic pressure resulting from the differential concentration of salts on the opposing sides of the membrane. Under an unpressurized situation osmotic pressure would cause solvent on the side with the lower salt concentration to permeate to the side having the higher salt concentration. Hence, pressure must be applied to the solution being separated in order to overcome this osmotic pressure, and to cause a reasonable flux of solvent permeate. RO membranes typically exhibit satisfactory flow rates, or fluxes, at reasonable pressures. Currently, typical commercial RO systems have fluxes on the order of 15 to 50 lmh (liters per m2 per hour) at about 7 to 30 atmospheres pressure, depending on the application. Home RO systems typically run at lower pressures (1-6 atmospheres depending on line pressure) and lower fluxes (5 to 35 lmh). Seawater desalination typically runs at higher pressures (40 atm to 80 atm) and fluxes in the range of 10 lmh to 30 lmh. RO membranes also have advantageous salt retention characteristics. For example, to purify seawater, an RO membrane will typically have a salt retention value of at least 98.5 percent and preferably 99 percent or more, such that the total ion retention ability for commercial RO treatment of seawater typically will be in excess of 99.5%.
The majority of semipermeable membranes functioning as RO and NF membranes are cellulose acetate and polycarboxamide (hereinafter polyamide) membranes as well as sulfonated polysulfone and other membranes for NF alone. Polyamide membranes often are constructed as composite membranes having the thin polyamide film formed as a coating or layer on top of a supporting polysulfone microporous membrane. Typically, the RO or NF membrane is formed by interfacial polymerization or by phase inversion deposition. For example, U.S. Pat. No. 3,744,642 to Scala discloses an interfacial membrane process for preparation of an RO or NF membrane. Additional U.S. patents disclosing polyamide and polysulfonamide membranes include U.S. Pat. Nos. 4,277,344; 4,761,234; 4,765,897; 4,950,404; 4,983,291; 5,658,460; 5,627,217; and 5,693,227.
Several characteristics are described in these and other U.S. patents pertaining to semipermeable membranes as factors for advantageous operation of RO and NF membranes. These characteristics include high durability, resistance to compression, resistance to degradation by extremes of pH or temperature, resistance to microbial attack, and stability toward potentially corrosive or oxidative constituents in feed water such as chlorine. Although the polyamide membranes typified by U.S. Pat. No. 4,277,344 are widely used, especially in desalination operations to purify water, these membranes are susceptible to corrosive attack, as well as low pH and temperature degradation. Furthermore, microbial fouling of the membrane can cause loss of flux and/or retention characteristics. Nevertheless, current polyamide membranes substantially reach the goals of minimal thickness and substantial freedom from flaws or imperfections, allowing for widespread commercial use.
These two goals of minimal thickness and freedom from flaws, however, are not altogether compatible. As the thickness of the polymeric film or membrane decreases, the probability of defect holes or void spaces in the film structure increases significantly. The defect holes or void spaces result in significant loss of solute retention.
Polysulfonamide membranes provide several possible advantages over polyamide membranes. Although polysulfonamide membranes have been reported, they have no appreciable commercial application. Generally they have poor flux rates and low solute retention capabilities. For example, B. J. Trushinski, J. M. Dickson, R. F. Childs, and B. E. McCarry have described investigations of polysulfonamide membranes and their modifications in the course of attempts to achieve higher flux and better retention abilities. Trushunski, Dickson, Childs, and McCarry report these attempts in the Journal of Membrane Science 143, 181 (1998); Journal of Applied Polymer Science, 48, 187 (1993); Journal of Applied Polymer Science, 54, 1233 (1994); and Journal of Applied Polymer Science, 64, 2381 (1997). Trushunski, Dickson, Childs, and McCarry however, have been unable to achieve the functional properties of the polyamide membranes using polysulfonamides. Those functional properties are believed to enable at least in part the achievement of the typical performance thresholds qualifying a membrane for practical use.
Therefore there is a need for polysulfonamide membranes that display flux and retention capabilities like those of the polyamide membranes. In addition, there is a need to develop semipermeable membranes such as RO and NF membranes that are stable to strong acid conditions and/or stable to oxidative conditions. There is a further need to develop semipermeable membranes that will be useful in heavy, corrosive industrial applications including mineral mining, industrial desalination, industrial waste purification, industrial and residential recycling and solute recovery.
These needs are met by the present invention, which provides a sulfonamide polymer matrix, which, when configured as a semipermeable membrane, exhibits improved flux, improved retention properties, and/or improved stability. The invention also provides a process for preparing a sulfonamide polymer matrix of the invention.
More specifically, the present invention is directed to the following developments:
1. a sulfonamide polymer matrix;
2. a membrane including such a matrix;
3. a composite membrane including such a matrix;
4. an article including a combination of the sulfonamide polymer matrix and a support material;
5. a process for preparing the sulfonamide polymer matrix;
6. a process for preparing a membrane or a composite membrane of the invention
7. a polysulfonamide matrix, membrane, or composite membrane made according to the process of the invention;
8. a polysulfonamide matrix formed of a polymeric reaction product of a compound having at least two reactive sulfonyl groups and an amine compound having at least two reactive primary amine groups and at least one secondary or tertiary amine group;
9. use of a polysulfonamide membrane of the invention to separate components of a fluid mixture;
10. a process for separation of such fluid mixtures;
11. a polysulfonamide membrane that is stable under low pH conditions or corrosive or oxidative conditions;
12. an apparatus or device including the matrix or the membrane; and
13. use of the sulfonamide matrix as a coating.
The sulfonamide polymer matrix is composed of sulfonyl compound residues having at least two sulfonyl moieties and amine compound residues having at least two amine moieties wherein the sulfonyl and amine moieties form at least some sulfonamide groups (xe2x80x94SO2xe2x80x94N(R)xe2x80x94). Preferably the amine compound residue having at least two amine moieties is not polyethyleneimine having a molecular weight of greater than or equal to 600 daltons. More preferably, the amine compound residue having at least two amine moieties is not polyethyleneimine having a molecular weight of greater than or equal to 500 daltons. Even more preferably, the amine compound residue having at least two amine moieties is not polyethyleneimine having a molecular weight of greater than or equal to 400 daltons.
The sulfonamide polymer contains at least some sulfonamide linkages in the backbone of the polymer molecules (polymer-SO2xe2x80x94N(R)-polymer). Other functional and/or nonfunctional linkages (i.e. optional linkages) such as amide, ester, ether, amine, urethane, urea, sulfone, carbonate, and carbon-carbon sigma bonds derived from olefins may also optionally be present in the backbone. The preferable backbone linkages are sulfonamide linkages, optionally also containing amide, amine, carbon-carbon, ether and/or sulfone linkages. Especially preferably, a sulfonamide linkage backbone with one or more of the optional linkages is stable to low pH conditions. Also, the amount of optional linkages is preferably no more than about 50 percent, 30 percent, or 10 percent, and more preferably, no more than about 5 percent of the number of sulfonamide linkages present in the sulfonamide polymer backbone.
Preferably, the sulfonamide matrix may be at least partially cross-linked. Preferably, the cross-linking is achieved though inclusion of at least some of the sulfonyl compound residue and/or the amine compound residue as residues having three or more groups. Preferably, the sulfonyl compound residues include some portion of compound with at least three sulfonyl groups and/or amine groups so that polymer chains are cross-linked. Preferably, the sulfonamide polymer of the matrix is an interfacial polymer. In further preferred embodiment of the sulfonamide matrix, the matrix is free of polymer derived from an aqueous latex of sulfonamide polymer. Additionally, the matrix is preferably free of sulfonamide polymer derived from a polyalkylamine (e.g. polyethyleneamine). In another preferred embodiment, the invention provides a matrix wherein the polymer on one side of the matrix contains at least some sulfonic acid groups, and/or the polymer on the opposite side or on one side of the matrix contains at least some amine groups.
The polymer matrix according to the invention is preferably formed at least in part from compound residues derived from a sulfonyl compound having any organic nucleus and at least two activated sulfonyl groups. The sulfonyl compound may be a polymer, monomer, an oligomer, a complex molecule or other organic moiety having at least two activated sulfonyl groups. Preferably, this sulfonyl compound has Formula I:
Xxe2x80x94SO2xe2x80x94Zxe2x80x94(SO2xe2x80x94X)nxe2x80x83xe2x80x83I
wherein Z may be any organic nucleus that does not react with activated sulfonyl groups or with primary amine groups and X is any leaving group appropriate for creation of activated sulfonyl groups. An activated sulfonyl group is a sulfonyl group that will react with a primary or secondary amine group to produce a sulfonamide group. Preferably, Z is an organic nucleus of 1 to about 30 carbon atoms, which optionally may contain oxygen, sulfur and/or nitrogen atoms as substituents or within the nucleus structure itself. The organic nucleus preferably may be aliphatic (i.e., linear or branched alkyl or alkenyl or alkynyl), cycloaliphatic, aryl, arylalkyl, heteroaliphatic, heterocycloaliphatic, heteroaryl or heteroarylalkyl wherein the hetero nucleus contains one or more oxygens, sulfurs or nitrogens. The organic nucleus may be unsubstituted or substituted wherein the substituents are polar, ionic or hydrophobic in nature. Such substituents may include but are not limited to halogen, nitrile, alkyl, alkoxy, amide, ester, ether, amine, urethane, urea, carbonate and/or thioether groups optionally substituted with aliphatic groups of 1 to 6 carbons. Such substituents may also include but are not limited to halogen, carboxylic acid, sulfonic acid, phosphoric acid, and/or aliphatic groups of 1 to 12 carbons, the latter aliphatic groups optionally being substituted by halogens. The term xe2x80x9cnxe2x80x9d may be an integer of from 1 to 3. X may be halogen, azide, a mixed sulfonoxy group (forming an activated sulfonyl anhydride) or the like.
The polymer matrix of the invention preferably may also be formed from amine compound residues derived from an amine compound having any organic nucleus and at least two primary and/or secondary amine groups. The amine compound may be a polymer, monomer, an oligomer, a complex molecule or any organic moiety having at least two primary and/or secondary amine groups. Preferably, the amine compound has Formula II:
R1xe2x80x94NHxe2x80x94Yxe2x80x94[(CH2)j(NHxe2x80x94R2)]mxe2x80x83xe2x80x83II
wherein R1 and R2 are independently hydrogen or aliphatic groups of 1 to 30 carbons, Y is any appropriate organic nucleus, preferably of 1 to 30 carbons, and optionally containing one or more oxygen, sulfur or nitrogen atoms. Preferably, Y is an aliphatic, aryl or arylalkyl group of 1 to 30 carbons or is a corresponding heteroaliphatic, heteroaryl or heteroarylalkyl group containing 1 or more oxygen, sulfur or nitrogen atom. The letter m is an integer from 1 to 3 and j is zero or an integer of from 1 to about 10.
An especially preferred sulfonamide polymer matrix of the invention is formed from one or more combinations of the following compound residues: naphthalene disulfonyl residues of any substitution pattern, naphthalene trisulfonyl residues of any substitution pattern, benzene disulfonyl residues of any substitution pattern, benzene trisulfonyl residues of any substitution pattern, pyridine disulfonyl residues of any substitution pattern, alpha, omega diaminoalkanes of 1 to 10 carbons, ethylene diamine, triethylenetetramine, tetraethylene pentamine, tris(2-aminoethyl)methane and tris-(2-aminoethyl)amine, meta-xylene diamine, 2-hydroxy-1,3-diaminopropane. As a second development, the invention includes a polysulfonamide membrane. The invention also includes a composite membrane including a sulfonamide polymer matrix of the invention located on at least one side of a porous or microporous support material. The porous support material may be composed of any suitable porous material including but not limited paper, modified cellulose, interwoven glass fibers, porous or woven sheets of polymeric fibers and other porous support materials made of polysulfone, polyethersulfone, polyacrylonitrile, cellulose ester, polyolefin, polyester, polyurethane, polyamide, polycarbonate, polyether, and polyarylether ketones including such examples as polypropylene, polybenzene sulfone, polyvinylchloride, and polyvinylidenefluoride. Ceramics, including ceramic membranes, glass and metals in porous configurations are also included. The support material typically contains pores have sizes ranging from about 0.001 microns to about 1 micron. The composite membrane may be formed as sheets, hollow tubes, thin films, or flat or spiral membrane filtration devices. The support thickness dimension ranges from about 1 micron to approximately 500 microns (preferably, about 1 micron to approximately 250 microns), with the upper boundary being defined by practical limitations.
The polysulfonamide membrane of the invention has an independent A value and independent retention value that enables it to operate in a practical setting. Its A value and retention value bring the composite membrane within the ranges achieved by polyamide membranes. Either as an RO or an NF membrane, the polysulfonamide composite membrane of the present invention preferably has an water permeability A value of at least 2 or 3 when the A value is the sole parameter being used to describe the membrane. When used as an RO membrane, the polysulfonamide composite membrane of the present invention preferably has an NaCl retention value of at least 98 percent when the retention value is the sole parameter being used to describe the membrane. In combinations of A value and retention value, the polysulfonamide composite membrane of the present invention has an A value from at least about 1 to at least about 20 and a corresponding NaCl retention of at least about 99 percent down to about 10 percent.
When used as an NF membrane to retain magnesium sulfate and pass sodium chloride, the retention values regarding separate magnesium sulfate and sodium chloride salts challenges ranges from at least about 90 to at least about 95 percent retention of magnesium sulfate with at least 50 to at least about 75 percent transmission of sodium chloride. For separate magnesium sulfate and magnesium chloride tests, the retention/transmission values are at least about 90 to at least about 95 percent and at least about 30 to at least about 60 percent respectively. For separate sodium sulfate and magnesium chloride tests, the retention/transmission values range from at least about 90 to at least about 95 percent and at least about 30 percent to at least about 60 percent respectively. For separate sodium sulfate, sodium chloride tests, the retention/transmission values are at least about 90 to at least about 95 percent and at least about 50 to at least about 75 percent respectively.
As a third development, the invention includes a combination of the matrix layered or coated upon the surface of any substrate including but not limited to a porous bead, a chromatographic material, metal surfaces, a microdevice, a medical device, a catheter, a CD coating, a semiconductor wafer, digital imaging printing media, a photoresist layer and the like.
As a fourth development, the invention includes a process for preparing the sulfonamide polymer matrix. The process includes the step of contacting a first phase including an amine compound having at least two amine groups which are capable of forming sulfonamide bonds, with a second phase including a sulfonyl compound having at least two sulfonyl groups which are capable of forming sulfonamide bonds.
The first and second phases may be miscible or immiscible in each other. If miscible, the two phases may mix at least to some extent, and preferably to a significant extent upon contact. If immiscible, the two phases may mix at least to some extent or may not mix at all. Preferably these phases are at least substantially immiscible in each other, and especially preferably nearly completely immiscible in each other.
The first and second phases may be neat starting materials or they may include one or more solvents.
The time for formation of the matrix resulting from contact of the phases is sufficient to generate the matrix as a barrier to further sulfonamide production and is also typically short. As explained above the rapidity with which the matrix is formed bears upon its thickness, density and defect parameters. Preferably the time for matrix formation ranges up to about 800 seconds or up to about 480 seconds, or more preferably up to about 240 seconds or about 120 seconds. The rate of reaction between the sulfonyl compound and the amine compound may be promoted through the use of a catalyst, heat, and/or other reaction acceleration technique. Preferably, the first or second phase includes a catalyst for promotion of sulfonamide bond formation. Preferably, the catalyst is a Lewis base nucleophile such as a nitrogen, phosphorus inorganic or organic compound.
As a fifth development, the invention includes the polysulfonamide membrane or composite membrane prepared according to a process of the invention.
As a sixth development, the invention includes certain polymeric formulas for the sulfonamide polymer matrix. These formulas involve the polymeric reaction product of an aromatic or aliphatic compound having at least two active sulfonyl groups and amine compound having at least two active primary groups and also at least one secondary or tertiary amine group positioned between the two primary amine groups. The semipermeable membrane embodiment of this development is especially useful under harsh acidic conditions (pHxe2x89xa63).
As a seventh development, the invention involves the use of the foregoing membranes for separation of a fluid mixture into its permeate and retentate. The fluid mixture may contain a mixture of inorganic salts, similar small organic molecules, a low pH and/or corrosive or oxidative substances. The separated permeate may be water or purified organic liquid. The retentate preferably will contain the solute.
As an eighth development, the invention includes a process for separation of a fluid mixture. This process uses the polysulfonamide membrane of the invention to separate the fluid mixture into a permeate and a retentate.
As a ninth development, the invention includes the performance of the polysulfonamide membrane of the invention under harsh conditions such as but not limited to extreme pH, temperature, and/or oxidative conditions. The NF polysulfonamide membrane of the invention is capable of performing significant separation of alkaline, alkaline earth, and transition metal ions as salts from feed solutions that are acidic and/or contain corrosive materials. The NF polysulfonamide membrane of the invention is capable of retaining certain metal ons as inorganic salts while allowing the neutral, acidic, or basic aqueous medium to permeate. Additionally, the membranes of the invention are capable of separating components and/or separating solvent from dissolved solids components of such feed solutions as may come from the mineral separation industry, the paints and coatings industry, the food and cosmetics industry, the metals and fabrication industry, and the plastics industry as well as others. Preferably the polysulfonamide membranes of the invention will continue to perform significant separation from a feed solution even though the feed solution contains strong acids such as sulfuric acid, nitric acid, hydrochloric acid and the like.
As a tenth development, the invention includes an apparatus or device for separation of solutes from a feed solution. The apparatus or device includes a polysulfonamide matrix of the invention (e.g. a membrane or a composite membrane).
As an eleventh development, the invention includes the use of the matrix as an adhesive promoter, a surface lubricant, a chemically resistant coating, or a photoresist.
As a twelveth development, it has been discovered that a sulfonamide polymer matrix comprising 1,3,5-benzenetrisulfonyl residues and alkyldiamine residues wherein some of the 1,3,5-benzenetrisulfonyl residues and alkyldiamine residues form sulfonamide groups in the polymer backbone, possesses an unexpected and advantageously high level of stability toward oxidative conditions. Accordingly, one preferred aspect of the invention provides a sulfonamide polymer matrix comprising 1,3,5-benzenetrisulfonyl residues and alkyldiamine residues, wherein some of the 1,3,5-benzenetrisulfonyl residues and alkyldiamine residues form sulfonamide groups in the polymer backbone. The alkyldiamine can preferably be a compound of formula II: R1xe2x80x94NHxe2x80x94Yxe2x80x94[(CH2)j(NHxe2x80x94R2)]m; wherein Y is C1-C18alkyl; each R1 and R2 is hydrogen; m is 1; and j is zero. Preferably, Y is C1-C10alkyl; and more preferably, Y is C1-C16alkyl. Most preferably, the alkyldiamine is ethanediamine.
Definitions
Unless otherwise stated, the following definitions apply.
The term xe2x80x9cmatrixxe2x80x9d means a regular, irregular and/or random arrangement of polymer molecules. The molecules may or may not be cross-linked. On a scale such as would be obtained from SEM, x-ray or FTNMR, the molecular arrangement may show a physical configuration in three dimensions like those of networks, meshes, arrays, frameworks, scaffoldings, three dimensional nets or three dimensional entanglements of molecules. The matrix is usually non-self supporting and most often is constructed as a coating or layer on a support material. The sulfonamide polymer matrix has an average thickness from about 5 nm to about 600 nm, preferably about 5 to about 400 nm. In usual practice, the matrix is grossly configured as an ultrathin film or sheet. More preferably, the matrix has an average thickness from about 5 nm to about 100 nm, or from about 15 nm to about 100 nm, or from about 25 nm to about 90 nm.
The term xe2x80x9cmembranexe2x80x9d means a semipermeable matrix.
The term xe2x80x9ccomposite membranexe2x80x9d means a composite of a matrix layered or coated on at least one side of a porous support material.
The term xe2x80x9csupport materialxe2x80x9d means any substrate onto which the matrix can be applied. The substrate may be porous or non-porous. Included are semipermeable membranes especially of the micro- and ultrafiltration kind, metal, ceramic, fabric, plastic, wood, masonry, building materials, electronic components, medical components, filtration materials as well as others.
The term xe2x80x9cstable,xe2x80x9d when used to characterize a membrane in acid, means that substantially all of the membrane remains intact after exposure to a solution of about 20% sulfuric acid for one day at 90xc2x0 C. or 30 days at 40xc2x0 C., preferably very substantially all of the membrane remains intact under these conditions and especially preferably essentially all of the membrane remains intact under these conditions. In this context of acid treatment, the terms xe2x80x9csubstantially all, very substantially all and essentially allxe2x80x9d mean respectively that the membrane maintains at least 90%, at least 95%, at least 99% of its sulfur-nitrogen sulfonamide bonds after it has been exposed to these conditions. Also, maintaining at least substantially all of the sulfur-nitrogen sulfonamide bonds in certain membrane situations includes an improvement of the original permeation and retention values of the membrane such that the after-test permeation and retention values may be better than the original values.
The term xe2x80x9cpolyamidexe2x80x9d means a polymer having a backbone of repeating carboxamide groups all of the same arrangement (xe2x80x94CONHxe2x80x94) or of alternating reverse arrangement (xe2x80x94CONHxe2x80x94Rxe2x80x94NHCOxe2x80x94). The term does not include polymers having sulfonamide groups in the backbone (polymer-SO2xe2x80x94N-polymer).
The term xe2x80x9c20% sulfuric acidxe2x80x9d means a solution of deionized water and 20% sulfuric acid by weight.
The term xe2x80x9caverage thicknessxe2x80x9d is the average matrix cross-sectional dimension. It means the average distance in cross section from one side of the matrix to the opposite side of the matrix. Since the matrix has surfaces that are at least some extent uniform, the average thickness is the average distance obtained by measuring the cross-sectional distance between the matrix sides. Techniques such as ion beam analysis, X-ray photoelectron spectroscopy (XPS), and scanning electron microscopy (SEM) can be used to measure this dimension. Because the cross-sectional dimension usually is not precisely the same at all points of the matrix, an average is typically used as an appropriate measurement. The preferred technique for measuring this dimension is SEM.
The term xe2x80x9cpermeationxe2x80x9d means transmission of a material through a membrane.
The term xe2x80x9cA valuexe2x80x9d in the context of the present invention represents the water permeability of a membrane and is represented by the cubic centimeters of permeate water over the square centimeters of membrane area times the seconds at the pressure measured in atmospheres. An A value of 1 is essentially 10xe2x88x925 cm3 of permeate over the multiplicand of 1 centimeter squared of membrane area times 1 second of performance at a net driving pressure of one atmosphere. In the context of the present invention, A values given herein have the following unit designation: 10xe2x88x925 cm3/(cm2.sec.atm.) or 10xe2x88x925 cm/(sec.atm) at 25 xc2x0 C.
A=permeate volume/(membrane area*time*net driving pressure).
The term xe2x80x9crecovery valuexe2x80x9d means the ratio of permeate fluid flow to feed fluid flow, expressed as a percentage. It should be noted that under most circumstances the flux is directly related to the applied trans-membrane pressure, i.e., a membrane can provide a specific flux of permeate at a given pressure. This flux is often given in units of lmh.
The term xe2x80x9cnet driving pressurexe2x80x9d is equal to the average trans-membrane pressure minus the feed-permeate osmotic pressure difference.
The term xe2x80x9ctransmission valuexe2x80x9d means the solute concentration in the permeate divided by the average of the solute concentration in the feed and in the concentrate, expressed as a percentage [i.e. transmission value=permeate/((feed+concentrate)/2), expressed as a percentage]. The concentrate is the fluid that flows completely past, but not through, the membrane. The term xe2x80x9cretention valuexe2x80x9d means, in the context of the present invention, 100% minus the transmission value. The term xe2x80x9cpassagexe2x80x9d or xe2x80x9c% Passxe2x80x9d is equivalent to the transmission value. Unless otherwise stated, the retention and transmission values are achieved by passing a 1800 to 2200 ppm solution of the specified solute in DI water at a pH of 6.5 to 7.5, at 24-26 degrees C., at 221-229 psi transmembrane pressure, at a recovery value of less than 2%, at a Renyolds number of at least 2000 across the membrane, and by collecting permeate samples for permeation analysis between the first and second hour of testing. The term xe2x80x9crecovery valuexe2x80x9d means, in the context of the present invention, the ratio of permeate fluid flow to feed fluid flow, expressed as a percentage.
The term xe2x80x9caliphaticxe2x80x9d or xe2x80x9caliphatic groupxe2x80x9d is known in the art and includes branched or unbranched carbon chains which are fully saturated or which comprise one or more (e.g. 1, 2, 3, or 4) double or triple bonds in the chain. Typically, the chains comprise from 1 to about 30 carbon atoms. Preferably, the chains comprise from 1 to about 20 carbon atoms, and more preferably, from 1 to about 10 carbon atoms. Representative examples include methyl, ethyl, propyl, isopropyl, pentyl, hexyl, propenyl, butenyl, pentenyl, propynyl, butynyl, pentynyl, hexadienyl, and the like.
The term xe2x80x9ccycloaliphaticxe2x80x9d or xe2x80x9ccycloaliphatic groupxe2x80x9d is known in the art and includes mono-cyclic and poly-cyclic hydrocarbons which are fully saturated or which comprise one or more (e.g. 1, 2, 3, or 4) double or triple bonds in the ring(s). Such groups comprise from 1 to about 30 carbon atoms. Preferably, from 1 to about 20 carbon atoms, and more preferably, from 1 to about 10 carbon atoms. Representative examples include cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, cyclopentenyl, cyclohexenyl, and the like.
The term xe2x80x9carylxe2x80x9d denotes a phenyl radical or an ortho-fused bicyclic carbocyclic radical having about nine to ten ring atoms in which at least one ring is aromatic. Representative examples include phenyl, indenyl, naphthyl, and the like.
The term xe2x80x9cheteroarylxe2x80x9d denotes a group attached via a ring carbon of a monocyclic aromatic ring containing five or six ring atoms consisting of carbon and one to four heteroatoms each selected from the group consisting of non-peroxide oxygen, sulfur, and N(X) wherein X is absent or is H, O, (C1-C4)alkyl, phenyl or benzyl, as well as a radical of an ortho-fused bicyclic heterocycle of about eight to ten ring atoms derived therefrom, particularly a benz-derivative or one derived by fusing a propylene, trimethylene, or tetramethylene diradical thereto. Representative examples include furyl, imidazolyl, triazolyl, triazinyl, oxazoyl, isoxazoyl, thiazolyl, isothiazoyl, pyrazolyl, pyrrolyl, pyrazinyl, tetrazolyl, pyridyl, (or its N-oxide), thienyl, pyrimidinyl (or its N-oxide), indolyl, isoquinolyl (or its N-oxide) quinolyl (or its N-oxide), and the like.
The term xe2x80x9cheteroaliphaticxe2x80x9d or xe2x80x9cheteroaliphatic groupxe2x80x9d is known in the art and includes branched or unbranched carbon chains wherein the chain is interrupted with one or more (e.g. 1, 2, 3, or 4) non-peroxy oxygen, sulfur or nitrogen atoms. Typically, the chains comprise from 1 to about 30 carbon atoms and from about 1 to about 10 heteroatoms. Preferably, the chains comprise from 1 to about 20 carbon atoms and from about 1 to about 10 heteroatoms; and more preferably, from 1 to about 10 carbon atoms and from about 1 to about 5 heteroatoms. Representative examples include 2-methoxyethyl, 3-methoxypropyl, and the like.
The term xe2x80x9cheterocycloaliphaticxe2x80x9d or xe2x80x9cheterocyclicaliphatic groupxe2x80x9d is known in the art and includes mono-cyclic and poly-cyclic heterocycles which are fully saturated or which comprise one or more (e.g. 1, 2, 3, or 4) double bonds in the ring, and which comprise one or more (e.g. 1, 2, 3, or 4) non-peroxy oxygen, sulfur or nitrogen atoms in one or more ring. Typically, the rings comprise from 1 to about 30 carbon atoms and from about 1 to about 10 heteroatoms. Preferably, the chains comprise from 1 to about 20 carbon atoms and from about 1 to about 10 heteroatoms; and more preferably, from 1 to about 10 carbon atoms and from about 1 to about 5 heteroatoms. Representative examples include tetrahydrofuranyl, tetrahydrothiophenyl, pyrrolidinyl, piperidinyl, morpholinyl, and dihydropyranyl, and thiomorpholinyl, and the like.